As regards producing, storing and transporting/shipping liquid hydrocarbon-based fuels such as kerosene, it is known that they shall be contaminated with water due not only to contact with humid/moist air but also with storage containers and transporting conduits. Kerosene is hygroscopic and as a result attracts water. Once the solubility limit has been exceeded, first very fine water droplets form as an emulsion in the fuel base. Due to this hygroscopicity, the fine water droplets become larger and thereupon may settle at the bottom in the form of a closed sump phase. Accordingly both free and bound water is frequently present in fuels. Safety requires removing this water periodically to preclude damage in fuel-driven engines. Illustratively the suspended water may be separated by using coalescence separators.
Recently certain fuel additives have become problematic because hampering separating the water from the fuel. Occasionally human failure entails accidentally filling tank facilities with mixtures of fuel and water, or even with water only. In particular in the airline industry, especially high safety requirements must be met. Accordingly it is highly desirable to monitor the entire fuel supply chain from the refinery to tank filling and to rapidly detect both the content of free water and the presence of water instead of fuel and thereby to issue timely warnings and eliminate such dangers.
There are a number of solutions in the state of the art to the above cited difficulties. Both British patents 1,460,623 and 1,554,309 resort to means requiring a measuring chamber. Such designs incur the drawback that in the case of continuous measurements (British patent 1,460,623) only qualitative results are available, or, in the case of discontinuous measurements (British patent 1,554,309), they will result only in quantitative values. These designs do not disclose a detector able to continuously and quantitatively measure free water in fuel and simultaneously the presence of pure water in containers and conduits.
The Swiss patent disclosure 01635-05 discloses another applicable solution. The unit described therein relates to a probe to simultaneously measure light scattering and light absorption at a given wavelength, a first housing being fitted with windows to pass transmitted light respectively scattered light. This Swiss design further comprises a second housing which is closed at one end and is fitted with a recess receiving optical elements to guide and collimate light and having one window transparent to optical radiation. The housing windows are mutually opposite, the housings being linked to each other by a spacer element.